Brief
Oxford study suggests animals originated up to 200 million years earlier than fossil record shows
Analysis of microfossils from Mongolia challenges the assumption that animals appeared only shortly before the Cambrian.
By Felo News Desk · Published
Researchers led by the University of Oxford propose that animals may have evolved up to 200 million years before they appear clearly in the fossil record, according to a study published in Science Advances on Oct. 2.
What happened
The team examined more than 140 microfossil samples from the Kheseen Biota in Mongolia, a deposit that is roughly 40 million years younger than the well‑known 590‑million‑year‑old Weng'an Biota in China. Using scanning electron microscopy, they identified new microfossil species, including acritarchs and embryo‑like forms with internal cells, but none could be definitively classified as animals.
What the reports add
Science Daily notes that the Kheseen Biota, despite its exceptional preservation, lacks animal fossils even though animals are known from other sites worldwide by the time the deposit formed. The article contrasts this with the earlier assumption that the absence of animals in the older Weng'an Biota meant animals had not yet evolved.
What was said
Senior author Associate Professor Ross Anderson of Oxford’s Museum of Natural History said, "The Kheseen Biota breaks the argument that the exceptional microfossils of Weng'an mean we would have seen animal fossils in the assemblage had they existed at the time. The Kheseen microfossils are just as well‑preserved, yet animals continue to be absent – despite the fact we know at that point they existed."
How it came about
The study builds on decades of debate over the timing of animal origins. Earlier work used the lack of animal remains in the Weng'an Biota to set a maximum age for animal evolution. By analysing a younger but similarly preserved deposit, the Oxford team demonstrates that exceptional fossil preservation does not guarantee the capture of animal remains, suggesting that early animals may have lived in habitats or under chemical conditions that left little trace in such deposits.
Key facts
- The Oxford-led study examined over 140 microfossil samples from Mongolia's Kheseen Biota. (sciencedaily.com)
- No fossils from the Kheseen Biota can be confidently identified as animals, despite excellent preservation. (sciencedaily.com)
- Researchers argue this challenges the assumption that animals evolved only shortly before the Cambrian period. (sciencedaily.com)
Sources
- [1] sciencedaily.com — originally reported as “Animals may have evolved 200 million years earlier than we thought”
